Electromagnetic switch.



J. EATON. ELECTROMAGNETIC SWITCH. APPLICATIVON FILED AUG.4. 1913.

Patented Dec.28,1915.

Ply.

lnven tor John Eato Witnesses:

by QMA:

His Attorney.

UNITED STATES PATENT OFFICE.

JOHN EATON, OF\SCI-IENECTADY, NEW YORK, AssIGNon r0 GENERAL nrinornrcCOMPANY, A CORPORATION on NEW YORK.

ELECTROMAGNETIC SWITCH.

Specification of Letters Patent.

Patented Dec. 28, 1915.

Application filed August 4, 1913. Serial No. 782,794.

Electromagnetic Switches, of which the following is a specification.

This inventionrelates to electromagnetic switches, and has for itsobject the provision of a device of this character in which the contactscannot stick or freeze together under the most trying conditions ofservice.

In the operation of electromagnetic switches, especially as used in thecontrol of electric motors where the switches are operated veryfrequently and the currents are heavy, it occasionally happens that theare formed between the contacts fuses the metal and causes the contactsto stick together, due to the formation of a slight weld between them.This most frequently happens where the magnetizing winding is onlyinstantaneously energized so as to cause the contacts to just touch eachother without being actually forced into firm engagement. It alsosometimes happens because of the slow opening of the contacts due tovery slow decrease of magnetic pull and other causes. In the type ofcontact for' electromagnetic switches now well known, in which thecontacts slide or roll upon each other so as to produce a wiping action,any slight welding or sticking will be overcome by the wiping action ifthe contact is once wiped home. If, however, the contacts merely engageor kiss without being wiped to the final position, a weld might formwhich would hold the contacts in closed position against the tendency ofgravity or a spring to open the switch.

One of the objects of my invention is to overcome this difliculty andmake it practically impossible for the contacts of the switch to weldtogether in the manner above described. 1

In carrying out my invention I provide means whereby just before themovable contact reaches the fixed contact a spring is placed understress, tending to force the movable contact away from the fixed contactso that in case the contacts merely touch and tend to weld, the springwill force the contacts apart and break the weld. This I haveaccomplished in one embodiment. of my invention by the use of the springwhich is ordinarily used upon such switches for causing a yielding andwiping action of the contacts.

Other objects and purposes of my invention will appear in the course ofthe following specification in which I have shown my invention embodiedin concrete form'for purposes of illustration.

In the accompanying drawing, Figure 1 represents a side view of anelectromagnetic switch embodying my invention; and Fig. 2 a fragmentaryview showing the partsin a different position.

Referring to the drawings, it will be seen that I have, shown anelectromagnetic switch, the parts of which are of well known design,consisting of a magnetizing winding 10 having a magnetic frame includingthe core 11 and the plates 12 and 13 mounted upon an insulating base 14.Pivoted to the plate 12 is an armature member 15 cooperating with theupper end of the core 11. Pivoted to this armature member at 16 is acontact member comprising a contact arm 17 upon, which is mounted thecontact tip 18. his tip 18 cooperates with a fixed contact tip 19mounted upon the base 14. A

spring 20 is interposed between the member 15 and the contact arm 17 sothat when the contact 18 engages the contact 19 the spring will yield.In the particular switch illustrated, the arrangement is such that asthe contacts 18 and 19 engage each other, the spring 20 is compressedand the contacts roll upon each other to a certain extent until theyreach the final position shown in full lines in Fig. 1. It will beunderstood, of course, that my invention is not limited in itsapplication to a switcli having contacts arranged in this or any otherspecific manner. The armature member 15 is so arranged that it isnormally biased to open position, this tendency to open being caused bythe presence of the tail piece 15, so that when the magnetizing windingis denergized the parts assume the position shown;

the

, of travel toward the fixed contact to be in opposition to the stressof the spring 20. In the particular arrangement shown in, the drawingsthis result is brought about by an arm 21 projecting upward from thecontact arm 17 and engaging the adjustable stud constituting a stop 2:2.In Fig. 2"the parts are shown in the position in which the contact 18still has a short distance to travel. At this point it will be seen thatthe free movement of the contact arm is stopped by the engagement of thearm 21 with the stop 22. Further movement of the contact 18 must beagainst the tension of the spring 20, that is, the armature member 15will be pulled down by the Winding and the spring 20 placed undercompression to force the contact 18 against the fixed contact during theshort distance traveled by the contact 18 which is indicated in Fig. 2-;therefore the contact 18 is strongly spring pressed or biased away fromthe fixed contact 19 during this interval. The result is that in casethe contacts should get near enough to each other to forman arc and weldthe contacts without forcing them to full closed position" or should thecontacts leave each other so slowly as to are and weld together thestress of the spring 20 would be sufiicient to break the weld and allowthe contacts to open.

When, however, the contact 18 is forced into seen that the spring 20 hasa double funci t1on: first, to bias the contact 18 away from v the fixedcontact during its last increment of travel toward the fixed contact,and second, to yieldingly hold the contacts together after the contactsonce start to fully close.

While it have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of thepatent statutes, it should be understood that l do not limit myinvention thereto, since various modifications thereof will suggestthemselves to those skilled in the art without departing from messes thespirit of my invention, the scope of which isset forth .in the annexedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. An electromagnetic switch comprising a magnetizing winding, anarmature member having a contact resiliently mounted thereon, a fixedcontact, and means whereby the resiliency of said mounting tends toforce the movable contact away from the fixed contact just prior to itsengagement with the fixed contact and thereafter resiliently holds it inengagement with the fixed contact when the armature member is moved toits final position by said winding.

2. An electromagnetic switch comprising a magnetizing winding, anarmature member provided with a contact pivotally mounted thereon, aspring interposed between said contact and said member, a fixed contact,

and means whereby said spring tends to force the movable contact awayfrom the fixed contact just prior to its engagement with the fixedcontact and thereafter yieldingly holds it in engagement with the fixedcontact when the armature member is moved to its final position by saidwinding.

3. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, a contact arranged to move intoengagement with the fixedcontact upon the energization of the said winding, a spring acting uponsaid movable contact, and means whereby said spring tends to force themovable con tact away from the fixed contact prior to its engagementwith the fixed contact and thereafter yieldingly holds it in engagementwith the fixed contact when the movable contact is moved to finalposition by said winding;

4. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member having a contact movably mounted thereon andarranged to engage said fixed contact and move upon it in a directionsubstantially at right angles to the direction of movement of themovable member, and means whereby the movable contact is biased awayfrom the fixed contact when the armature member is near its finalposition and is biased toward the fixed contact when it is moved uponthe fixed contact by the further pull of the magnetizing wind- 5. Anelectromagnetic switch comprising a magnetizing wlndlng, a fixedcontact, an armature member having a spring pressed contact movablymounted thereon and arranged to engage said fixed contact and move uponit against the spring pressure in a direction substantially at rightangles to the directionv of movement of the armature member, and meanswhereby the spring is placed under stress when the movable contact isnear the fixed contact so as to give it a spring pressure away from thefixed contact said pressure being removed by the engagement of thecontacts.

6. An electromagnetic switch comprising a magnetizing winding, a fixedcontact, an armature member having a spring pressed contact movablymounted thereon arranged to be moved bysaid winding into engagement withsaid fixed contact under yielding pressure of said spring, and meanswhereby the free movement of the movable contact is stopped when itapproaches the fixed contact sothat further movement toward said contacttakes place in opposition to the tension of the spring. 7. Anelectromagnetic switch comprising a magnetizing winding, a fixedcontact, a

contact arranged to move into engagement with the fixed contact upon theenergization of said Winding, a spring acting upon one of said contacts,and means whereby said spring tends to force the movable contact awayfrom the fixed contact prior to its engagement with the fixed contactand thereafter yieldingly holds it in engagement with the fixed contactwhen the movable contact is moved to final position by said winding.

In witness whereof, I have hereunto set my hand this first day ofAugust, 1913.

JOHN EATON.

Witnesses:

BENJAMIN B. HULL, HELEN ORFORD.

